TWO NEW BRITISH NEMERTEANS. 553 



laciniiiB havfc! not neai'ly so gn-eat an extent as in the majority 

 of the group, where they reach almost or quite to the intestinal 

 region, 



A<>-ain, the epithelium lining the ciliated canal shows a 

 lower degree of specialisation than is the case in any other 

 Lineid. 



Though possessing many apparently primitive features 

 tending to connect the LineidtB with the Carinellidre, Micrella 

 yet shows evidence of specialisation in other organs. 



The extent of the rhynchoca3lom over the whole length of 

 the body is a feature common enough in the Lineidse, though 

 never found in a Protonemertine. The curious i-hj^ncho- 

 coelomic pockets find their closest parallel in those of certain 

 Metanemertines, such as^ Drepanophorus, though the intimate 

 connection established between rhynchocoelom and lateral 

 blood lacuna seems to suggest a comparison with the lateral 

 rhynchocoelom vessels found in Carinella, Carinoma, and 

 Cerebratulus (cf. Burger [5J, pi. xii, fig. 7 ; pi. xiv, fig. 4 ; 

 pi. xxiii, fig. 6) . Whilst, however, iji nil these cases the blood- 

 vessel projects into the rhynchocoelom, in Micrella the 

 rhynchocoelom projects into the blood lacuna. 



A caudal appendage is a feature characteristic of many 

 Lineidfe, though what its significance may be is very doubtful. 

 Burger regards it as "das stark und meist plotzlich verjungte 

 hintere Korperende " (5, p. 238), which apparently remains 

 in a more or less embryonic state, possibly reminiscent of 

 an ancestral condition in which the body was relatively much 

 longer. He holds that it contains prolongations of all the 

 organs and layers found in the intestinal region with the 

 single exception of the rhynchocoelom. Further, he finds 

 that the anus opens at its tip. Coe, however (4, p. 493), 

 found that the arms in Cerebratulus lacteus opened at 

 the posterior end of the bod}^ just below where the caudal 



' Somewliafc similar diverticula have been recently described by Montgomery 

 for another genus of Metanemerteans — Proneurotes. Here however they arise 

 as ventral outgrowtiis of tlic proboscis sheath. (' Zoo], Jalir. Abt. f. Svst..' 

 1897, |). 4.) 



Vol.. 44, I'AI.'T 4. — NEW SEKIKS. NN 



